Transport characterization of magnetic states in Superconductor/Ferromagnet Nb/Co multilayers

TL;DR

This study investigates the magnetic states in Nb/Co superconductor/ferromagnet multilayers using transport measurements, revealing a controllable noncollinear magnetic state that could enable novel superconducting devices.

Contribution

It introduces a combined experimental approach to characterize magnetic states in Nb/Co multilayers and identifies a reversible, non-hysteretic magnetic state suitable for device control.

Findings

Identification of the monodomain scissor-like magnetic state.

Demonstration of reversible tuning of magnetic orientation.

Potential for odd-frequency spin-triplet superconductivity.

Abstract

Employment of the non-trivial proximity effect in Superconductor/Ferromagnet (S/F) heterostructures for creation of novel superconducting devices requires an accurate control of magnetic states in complex thin-film multilayers composing such devices. In this work we study experimentally in-plane transport properties of micro-structured Nb/Co multilayers. We apply various experimental techniques for characterization of multilayers, including the anisotropic magnetoresistance, the Hall effect and the first-order-reversal-curves analysis. We demonstrate that a combination of those techniques can provide a detailed knowledge of the magnetic state of the multilayer. In particular, we identify the range of existence of the coherently rotating, monodomain scissor-like state. It is anticipated, that in this noncollinear magnetic state the unconventional odd-frequency spin-triplet order parameter should appear. The non-hystertic nature of this state allows reversible tuning of the magnetic orientation. Thus, we identify the range of parameters and the procedure for controllable operation of devices based on such S/F heterostructures.